1. Field of the Invention
The invention relates to a mechanism for the height adjustment of a height-adjustable furniture part of a height-adjustable item of furniture, and a method for this.
2. Discussion of the Related Art
From the prior art, items of furniture are known with automatically movable parts, such as for example desks or work tables with a height-adjustable table plate. It is known to realize such a height adjustment device by means of electric motors integrated into the table column. It is known, furthermore, for the operation of the integrated motors, to provide input elements which are arranged for example under the table plate. Such operating elements or input elements have different switches, for example respectively a switch for raising and lowering the table plate. Conventionally, in addition cables must be provided between operating element and table column, in order to connect the operating element with the table column or respectively with the electric motor which is integrated into the table column.
For operation of such a table, an operator, who carries out for example activities by hand/manually on the table plate, must direct one hand to the operating element, in order to actuate the corresponding switch for the desired control command. Furthermore, the operator must avert his eyes from his current activity and throw a glance at the operating element, in order to be able to locate the correct switch. This is because the switches for an upward or respectively downward movement usually lie adjacent to one another, so that an intuitive operation is not guaranteed.
For example, from DE 10 2013 107 053 A1 or DE 20 2014 005 160 U1 in addition height-adjustable tables are known, in which the table plate itself can be used as activation of a height adjustment of the table plate via a force sensor. In order to activate the force sensor, so that an application of pressure or traction on the table plate by the operator can be recognized as the triggering of the height adjustment of the table plate, an actuation unit is provided on the table plate, such as for example a proximity switch, an induction loop or a membrane switch, which delivers a signal to the control unit, by means of which it detects that the table is to be moved upward or downward. However, this system has the disadvantage that the table plate manufacturer has to incorporate or respectively add the actuation unit extra for this. Furthermore, these elements are expensive and are also usually at risk of being damaged owing to the installation site.
Furthermore, devices are known for the electrical height adjustment of tables, which can detect collisions of the moving table plate with rigid objects and subsequently terminate a movement of the plate. Such devices for collision detection have an integrated sensor, such as for example a piezo element, in order to be able to detect a striking of the table plate on rigid objects and subsequently to stop a movement of the table plate. Such devices for collision avoidance are necessary in order to be able to prevent damage to the table and to other objects, and in order to be able to avoid injuries to the operator and uninvolved persons.
From EP 1 460 914 B1 a device with adjustable elements is known, wherein a piezo element is provided in the device, which element, in the case of a detected collision, triggers a corresponding control signal for stopping or reversing the movement.
As such piezo elements can not detect any absolute forces, but rather only changes in force, in EP 2 583 586 B1 an improvement to the prior art was achieved in that instead of the piezo element a force sensor is used, which can also detect absolute load values onto a table plate.
The above-mentioned devices have the disadvantage that an operation of the height adjustment of the table plate must take place laboriously through the operation by means of a switch which is arranged anywhere on the table. Furthermore, the provision of a separate operating element is expensive, and a table construction becomes complex through the provision of cabling and of fastening possibilities for cables and operating elements.
Furthermore, an operator of the table, as mentioned above, must avert his eyes from his current activity and direct his gaze to the operating element, in order to subsequently be able to actuate the desired switch with his hand.